Piston ring



Patented Feb. 28, 1939 UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to piston rings. It is particularly directed to a combination compression and flre ring for a Diesel or gasoline engine.

An object of this invention is to provide a ring of the character described, which may be effectively used when overhauling an engine which has an outl of round or worn liner or cylinder wall at its highest point of ring travel, generally taperlng down to a point (depending on the bore and stroke of the piston) of one and one-half inches to two inches below the highest point of ring travel, the construction of the ring being such as to provide a good seal with the inner surface of the cylinder, to prevent gases above the ring from entering bet een the ring and cylinder, whereby the gases wi be forced behind the ring to exert a pressure tending to force the ring outwardly against the cylinder.

Another object of this invention is to provide a piston ring of the character described, having an upper surface tapered upwardly and inwardly and an outer surface tapered downwardly and inwardly, and of greater taper than the taper of the worn portion of the cylinder, whereby on the suction stroke the ring will adapt itself almost to the worn portion of the cylinder, and on the compression stroke, the upper outer peripheral corner of the ring will not strike the upper corner of the worn part of the cylinder.

Yet another object of this invention is to provide a strong and rugged piston ring of the character described, which shall be relatively inexpensive to manufacture and yet practical and efficient to a high degree in use.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

The invention accordingly consists in the features of construction, combinations of elements, and arrangement of parts which will be exempli- Iled in the construction hereinafter described, and of which the scope of application will be indicated in the following claims.

In ythe accompanying drawing, in which is shown one of the various possible illustrative embodiments of this invention,

Fig. 1 is an elevational. cross-sectional view of a portion of a cylinder and piston ring embodying the invention, illustrating the compression stroke;

Fig. 2 is a view similar to Fig. l, but illustrating the suction stroke;

Fig. 3 is a view similar to Fig. l, but illustrating a ring when about half its outer surface is worn to conform to the worn portion of the cylinder Fig. 4 is a view similar to Fig. 2, but illustrating the piston ring when the same has been worn; and

Fig. 5 is a view similar to Fig. 1, but illustrating a conventional piston ring.

Referring now in detail to the drawing, I 5 designates a liner or cylinder having a downwardly and inwardly tapered worn surface II at the upper height of the stroke of the piston .I2. The length of the worn portion depends upon the bore of the cylinder and stroke of thepiston, usually lo extending one and one-half to two inches below the upper end of the stroke of the uppermost piston ring. At the upper end of the worn tapered surface I I is a shoulder I4 indicating the highest point of ring travel. l

In the drawing, the piston I2 is shown to be formed with a ring groove I5 having an upper land I6 and a lower land I1, and an inner surface I8. The groove I5, shown in the drawing, is the uppermost groove on the piston I2. Within the groove is a re or compression piston ring 20 embodying the invention.

'I'he ring 20 is annular and has a flat annular horizontal bottom surface 2 I, adapted to be seated on the lower land I 'I of the groove I5 during the 25 compression stroke. The ring 20 has an outer surface 22, tapering downwardly and inwardly, and preferably of greater taper than the taper of the worn surface II of the liner or cylinder, so that the upper edge of the outer surface 22, desiga0 nated by letter H contacts the surface II.

'Ihe upper surface 24.of the ring 2l tapers upwardly and inwardly. The point T where a horizontal plane passing through the point H cuts the inner surface 26 of the ring 20 is .001 inch to .0015 35 inch below theupper edge 0 of the inner surface of the ring. The angle between the surfaces 22 and 24 is preferably about 88 degrees.

Since the upper edge H of lthe piston ring at the upper end of the outer surface 22 the worn surface II, no gases can enter between the piston ring and the cylinder from the top, the gases passing between the upper surface 24 ofthe ring, and the upper land I6 of groove I5, and between the inner surface 26 of the piston 45 ring, and the inner surface I8 of the groove causing pressure tending to force the ring against the liner for making a better seal.

Where a conventional piston ring 30 is used, as illustrated in Fig. 5 of the drawing, of rectangu- 50 lar, transverse cross-section', gases can enter the space 3| between the outer surface of the ring and the inner worn surface of the cylinder to equalize the outer pressure tending to keep the ring away from the cylinder wall. This condi- 6l contacts 40 grooves, and often causing the engine to developl blow-by or passage of gases into the crankcase. Such a condition, with the use of a conventional ring piston in Fig. 5, is due to ineffective sealing during travel of the ring on the worn surface Il, where the efficiency of the top or fire ring should be highest.

Such ineffective sealing is obviated withthe use of the improved piston ring 20, shown in the drawing, wherein the taper of the outer surface of the ring is downward and inward, as is also the taper of the worn surface Il of the cylinder.

By making the taper 22 somewhat greater than the taper Il, the upper edge of the piston ring contacts the surface Il, hence, effectively preventing passage of gases above the cylinder, from passing between the piston ring and the surface il. y l

In Fig. 2, the piston ring is shown during the suction stroke of the piston. During such stroke, the upper surface of the piston ring contacts the upper land of the groove i5. During said suction stroke, the outer surface 22 of the piston ring comes closer to the worn surface H of the liner; and furthermore, the clearance between the inner surface 26 of the piston ring and the inner surface I8 of the groove is greater at the bottom than at the top, due to the taper of the upper surface 24 of the ring.

Figs. 3 and 4 show a portion of the ring after it has been worn in about half of its surface. Due to the upward inclination or taper of the surface 24 of the piston ring, the upper edge H of the ring will not contact the inner edge A of the shoulder I4. n

It will thus be seen that there is provided a device in which the several objects of this invention are achieved, and which is Well adapted to meet the conditions of practical use.

As various possible embodiments might bey made of the `above invention, and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. A piston ring having a vhorizontal bottom surface, a cylindrical inner surface, an upwardly and inwardly tapering upper surface, and a downwardly and inwardly tapering outer surface.

2. A piston ring having a horizontal bottom surface, a cylindrical inner surface, an upwardly and inwardly tapering upper surface, and a downwardly and inwardly tapering outer surface, the distance between the upper edge of the inner surface of the piston ring and a horizontal plane passing through the upper edge of the outer surface o f said piston ring, being between .001 inch and .0015 inch.

3. A piston ring having a horizontal bottom surface, a cylindrical inner surface, an upwardly and inwardly tapering upper surface, and a downwardly and inwardly tapering outer surface, the distance between the upper edge of the inner surface of the piston ring and a horizontal plane passing through the upper edge of the outer surface of said piston ring, being between .001 inch and .0015 inch, there being an angle of 88 degrees between said outer and upper surfaces of said ring.

HANS MAACK. 

